Define the following terms:

(i) Observation is the value at a particular period of a particular variable.

(ii) Raw data is the data collected in its original form.

(iii) Frequency of an observation is the number of times a certain value or a class of values occurs.

(iv) Frequency distribution is the organisation of raw data in table form with classes and frequencies.

(v) Discrete frequency distribution is a frequency distribution where sufficiently great numbers are grouped into one class.

(vi) Grouped frequency distribution is a frequency distribution where several numbers are grouped into one class.

(vii) Class interval is the width of such a class. 

(viii) Class size is the difference between the upper and the lower values of a class.

(ix) Class limits are the smallest and the largest observations (data, events, etc.) in a class.

(x) True class limits are the actual class limits of a class.